Problem: Simplify the following expression: $x = \dfrac{10n}{7} - \dfrac{n}{10}$
Solution: In order to subtract expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $7$ and $10$ $\lcm(7, 10) = 70$ $ x = \dfrac{10}{10} \cdot \dfrac{10n}{7} - \dfrac{7}{7} \cdot \dfrac{n}{10} $ $x = \dfrac{100n}{70} - \dfrac{7n}{70}$ $x = \dfrac{100n -7n}{70}$ $x = \dfrac{93n}{70}$